electronicconfigurations a guide for a level students knockhardy publishing 2008 specifications
TRANSCRIPT
ELECTRONICCONFIGURATIONS
A guide for A level students
KNOCKHARDY PUBLISHING
2008 SPECIFICATIONS
ELECTRONIC CONFIGURATIONS
INTRODUCTION
This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards.
Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available.
Accompanying notes on this, and the full range of AS and A2 topics, are available from the KNOCKHARDY SCIENCE WEBSITE at...
www.knockhardy.org.uk/sci.htm
Navigation is achieved by...
either clicking on the grey arrows at the foot of each page
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CONTENTS• The Bohr Atom
• Levels and sub-levels
• Rules and principles
• Orbitals
• Rules for filling orbitals.
• The Aufbau principle
• Electronic configurations of elements 1 to 36
• Electronic configurations of ions
ELECTRONIC CONFIGURATIONS
Before you start it would be helpful to…
• Know that electrons can be found outside the nucleus in energy levels ( shells)
• Know the electronic configurations of the first 20 elements in 2,8,1 notation
ELECTRONIC CONFIGURATIONS
THE BOHR ATOM
Ideas about the structure of the atom have changed over the years. The Bohr theory thought of it as a small nucleus of protons and neutrons surrounded by circulating electrons.
Each shell or energy level could hold a maximum number of electrons.
The energy of levels became greater as they got further from the nucleus and electrons filled energy levels in order.
The theory couldn’t explain certain aspects of chemistry.
Maximum electrons per shell
1st shell 2
2nd shell 8
3rd shell 18
4th shell 32
5th shell 50
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3
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LEVELS AND SUB-LEVELS
PRINCIPAL ENERGY LEVELS
During studies of the spectrum of hydrogen it was shown that the energy levels were not equally spaced. The energy gap between successive levels got increasingly smaller as the levels got further from the nucleus. The importance of this is discussed later.
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LEVELS AND SUB-LEVELS
During studies of the spectrum of hydrogen it was shown that the energy levels were not equally spaced. The energy gap between successive levels got increasingly smaller as the levels got further from the nucleus. The importance of this is discussed later.
A study of Ionisation Energies and the periodic properties of elements suggested that the main energy levels were split into sub levels.
Level 1 was split into 1 sub level
Level 2 was split into 2 sub levels
Level 3 was split into 3 sub levels
Level 4 was split into 4 sub levels
SUB LEVELS
CONTENTSCONTENTS
PRINCIPAL ENERGY LEVELS
RULES AND PRINCIPLES
HEISENBERG’S UNCERTAINTY PRINCIPLE
“You cannot determine the position and momentum of an electron at the same time.”
This means that you cannot say exactly where an electron is. It put paid to the idea of electrons orbiting the nucleus in rings and introduced the idea of orbitals.
THE AUFBAU PRINCIPLE
“Electrons enter the lowest available energy level.”
PAULI’S EXCLUSION PRINCIPLE
“No two electrons can have the same four quantum numbers.”
Two electrons can go in each orbital, providing they are of opposite spin.
HUND’S RULE OF MAXIMUM MULTIPLICITY
“When in orbitals of equal energy, electrons will try to remain unpaired.”
Placing two electrons in one orbital means that, as they are both negatively charged, there will be some electrostatic repulsion between them. Placing each electron in a separate orbital reduces the repulsion and the system is more stable. It can be described as the “SITTING ON A BUS RULE”!
ORBITALS
An orbital is... a region in space where one is likely to find an electron.
Orbitals can hold up to two electrons as long as they have opposite spin; this is known as PAULI’S EXCLUSION PRINCIPAL.
Orbitals have different shapes...
ORBITALS
An orbital is... a region in space where one is likely to find an electron.
Orbitals can hold up to two electrons as long as they have opposite spin; this is known as PAULI’S EXCLUSION PRINCIPAL.
Orbitals have different shapes...
ORBITAL SHAPE OCCURRENCE
s spherical one in every principal level
p dumb-bell three in levels from 2 upwards
d various five in levels from 3 upwards
f various seven in levels from 4 upwards
ORBITALS
An orbital is... a region in space where one is likely to find an electron.
Orbitals can hold up to two electrons as long as they have opposite spin; this is known as PAULI’S EXCLUSION PRINCIPAL.
Orbitals have different shapes...
ORBITAL SHAPE OCCURRENCE
s spherical one in every principal level
p dumb-bell three in levels from 2 upwards
d various five in levels from 3 upwards
f various seven in levels from 4 upwards
An orbital is a 3-dimensional statistical shape showing where one is most likely to find an electron. Because, according to Heisenberg, you cannot say exactly where an electron is you are only able to say where it might be found.
DO NOT CONFUSE AN ORBITAL WITH AN ORBIT
SHAPES OF ORBITALS
s orbitals
• spherical
• one occurs in every principal energy level
SHAPES OF ORBITALS
p orbitals
• dumb-bell shaped
• three occur in energy levels except the first
SHAPES OF ORBITALS
d orbitals
• various shapes
• five occur in energy levels except the first and second
Orbitals are not filled in numerical order because the principal energy levels get closer together as you get further from the nucleus. This results in overlap of sub levels. The first example occurs when the 4s orbital is filled before the 3d orbitals.
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1 1s
22s
2p
4s
33s3p3d
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
ORDER OF FILLING ORBITALS
Orbitals are not filled in numerical order because the principal energy levels get closer together as you get further from the nucleus. This results in overlap of sub levels. The first example occurs when the 4s orbital is filled before the 3d orbitals.
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1 1s
22s
2p
4s
33s3p3d
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
1 1s
22s
2p
3d
33s3p4s
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
ORDER OF FILLING ORBITALS
Orbitals are not filled in numerical order because the principal energy levels get closer together as you get further from the nucleus. This results in overlap of sub levels. The first example occurs when the 4s orbital is filled before the 3d orbitals.
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1 1s
22s
2p
4s
33s3p3d
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
1 1s
22s
2p
3d
33s3p4s
44p
4d4f
PRINCIPAL ENERGY LEVELS
SUB LEVELS
ORDER OF FILLING ORBITALS
THE FILLING ORDER
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
HOW TO REMEMBER ...
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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This states that…
“ELECTRONS ENTER THE LOWEST AVAILABLE
ENERGY LEVEL”
THE ‘AUFBAU’ PRINCIPAL
The following sequence will show the ‘building up’ of the electronic structures of the first 36 elements in the periodic table.
Electrons are shown as half headed arrows and can spin in one of two directions
or
s orbitals
p orbitals
d orbitals
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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HYDROGEN
1s1
THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
Hydrogen atoms have one electron. This goes into a vacant orbital in the lowest available energy level.
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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HELIUM
1s2
THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
Every orbital can contain 2 electrons, provided the electrons are spinning in opposite directions. This is based on...
PAULI’S EXCLUSION PRINCIPLE
The two electrons in a helium atom can both go in the 1s orbital.
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
LITHIUM
1s orbitals can hold a maximum of two electrons so the third electron in a lithium atom must go into the next available orbital of higher energy. This will be further from the nucleus in the second principal energy level.
The second principal level has two types of orbital (s and p). An s orbital is lower in energy than a p.
1s2 2s1
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
BERYLLIUM
Beryllium atoms have four electrons so the fourth electron pairs up in the 2s orbital. The 2s sub level is now full.
1s2 2s2
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
BORON
As the 2s sub level is now full, the fifth electron goes into one of the three p orbitals in the 2p sub level. The 2p orbitals are slightly higher in energy than the 2s orbital.
1s2 2s2 2p1
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
CARBON
The next electron in doesn’t pair up with the one already there. This would give rise to repulsion between the similarly charged species. Instead, it goes into another p orbital which means less repulsion, lower energy and more stability.
1s2 2s2 2p2
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
NITROGEN
Following Hund’s Rule, the next electron will not pair up so goes into a vacant p orbital. All three electrons are now unpaired. This gives less repulsion, lower energy and therefore more stability.
1s2 2s2 2p3
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
OXYGEN
With all three orbitals half-filled, the eighth electron in an oxygen atom must now pair up with one of the electrons already there.
1s2 2s2 2p4
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
FLUORINE
The electrons continue to pair up with those in the half-filled orbitals.
1s2 2s2 2p5
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
NEON
The electrons continue to pair up with those in the half-filled orbitals. The 2p orbitals are now completely filled and so is the second principal energy level.
In the older system of describing electronic configurations, this would have been written as 2,8.
1s2 2s2 2p6
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
SODIUM - ARGON
With the second principal energy level full, the next electrons must go into the next highest level. The third principal energy level contains three types of orbital; s, p and d.
The 3s and 3p orbitals are filled in exactly the same way as those in the 2s and 2p sub levels.
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
SODIUM - ARGON
Na 1s2 2s2 2p6 3s1
Mg 1s2 2s2 2p6 3s2
Al 1s2 2s2 2p6 3s2 3p1
Si 1s2 2s2 2p6 3s2 3p2
P 1s2 2s2 2p6 3s2 3p3
S 1s2 2s2 2p6 3s2 3p4
Cl 1s2 2s2 2p6 3s2 3p5
Ar 1s2 2s2 2p6 3s2 3p6
Remember that the 3p configurations follow Hund’s Rule with the electrons remaining unpaired to give more stability.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
POTASSIUM
In numerical terms one would expect the 3d orbitals to be filled next.
However, because the principal energy levels get closer together as you go further from the nucleus coupled with the splitting into sub energy levels, the 4s orbital is of a LOWER ENERGY than the 3d orbitals so gets filled first.
1s2 2s2 2p6 3s2 3p6 4s1
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
CALCIUM
As expected, the next electron pairs up to complete a filled 4s orbital.
This explanation, using sub levels fits in with the position of potassium and calcium in the Periodic Table. All elements with an -s1 electronic configuration are in Group I and all with an -s2 configuration are in Group II.
1s2 2s2 2p6 3s2 3p6 4s2
‘Aufbau’
Principle
‘Aufbau’
Principle
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
SCANDIUM
With the lower energy 4s orbital filled, the next electrons can now fill the 3d orbitals. There are five d orbitals. They are filled according to Hund’s Rule -
BUT WATCH OUT FOR TWO SPECIAL CASES.
1s2 2s2 2p6 3s2 3p6 4s2 3d1
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
TITANIUM
1s2 2s2 2p6 3s2 3p6 4s2 3d2
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
The 3d orbitals are filled according to Hund’s rule so the next electron doesn’t pair up but goes into an empty orbital in the same sub level.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
VANADIUM
The 3d orbitals are filled according to Hund’s rule so the next electron doesn’t pair up but goes into an empty orbital in the same sub level.
1s2 2s2 2p6 3s2 3p6 4s2 3d3
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
CHROMIUM
One would expect the configuration of chromium atoms to end in 4s2 3d4.
To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d to give six unpaired electrons with lower repulsion.
1s2 2s2 2p6 3s2 3p6 4s1 3d5
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
MANGANESE
The new electron goes into the 4s to restore its filled state.
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d5
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
IRON
Orbitals are filled according to Hund’s Rule. They continue to pair up.
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d6
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
COBALT
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d7
Orbitals are filled according to Hund’s Rule. They continue to pair up.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
NICKEL
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1s2 2s2 2p6 3s2 3p6 4s2 3d8
Orbitals are filled according to Hund’s Rule. They continue to pair up.
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
COPPER
One would expect the configuration of chromium atoms to end in 4s2 3d9.
To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d.
1s2 2s2 2p6 3s2 3p6 4s1 3d10
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
ZINC
The electron goes into the 4s to restore its filled state and complete the 3d and 4s orbital filling.
1s2 2s2 2p6 3s2 3p6 4s2 3d10
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
GALLIUM - KRYPTON
The 4p orbitals are filled in exactly the same way as those in the 2p and 3p sub levels.
HUND’S RULEOF
MAXIMUM MULTIPLICITY
HUND’S RULEOF
MAXIMUM MULTIPLICITY
1 1s
22s
2p
4s
3
3s
3p
3d
44p
4d
4f
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THE ELECTRONIC CONFIGURATIONS OF THE FIRST 36 ELEMENTS
GALLIUM - KRYPTON
Ga - 4p1
Ge - 4p2
As - 4p3
Se - 4p4
Br - 4p5
Kr - 4p6
Remember that the 4p configurations follow Hund’s Rule with the electrons remaining unpaired to give more stability.
Prefix with…
1s2 2s2 2p6 3s2 3p6 4s2 3d10
1s1
1s2
1s2 2s1
1s2 2s2
1s2 2s2 2p1
1s2 2s2 2p2
1s2 2s2 2p3
1s2 2s2 2p4
1s2 2s2 2p5
1s2 2s2 2p6
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s2
1s2 2s2 2p6 3s2 3p1
1s2 2s2 2p6 3s2 3p2 1s2 2s2 2p6 3s2 3p3 1s2 2s2 2p6 3s2 3p4
1s2 2s2 2p6 3s2 3p5
1s2 2s2 2p6 3s2 3p6
1s2 2s2 2p6 3s2 3p6 4s1
1s2 2s2 2p6 3s2 3p6 4s2 1s2 2s2 2p6 3s2 3p6 4s2 3d1
1s2 2s2 2p6 3s2 3p6 4s2 3d2
1s2 2s2 2p6 3s2 3p6 4s2 3d3
1s2 2s2 2p6 3s2 3p6 4s1 3d5
1s2 2s2 2p6 3s2 3p6 4s2 3d5
1s2 2s2 2p6 3s2 3p6 4s2 3d6
1s2 2s2 2p6 3s2 3p6 4s2 3d7
1s2 2s2 2p6 3s2 3p6 4s2 3d8
1s2 2s2 2p6 3s2 3p6 4s1 3d10
1s2 2s2 2p6 3s2 3p6 4s2 3d10
HHeLiBeBCNOFNeNaMgAlSiPSClArKCaScTiVCrMnFeCoNiCuZn
ELECTRONIC CONFIGURATIONS OF ELEMENTS 1-30
ELECTRONIC CONFIGURATION OF IONS
• Positive ions (cations) are formed by removing electrons from atoms• Negative ions (anions) are formed by adding electrons to atoms• Electrons are removed first from the highest occupied orbitals (EXC. transition
metals)
SODIUM Na 1s2 2s2 2p6 3s1 1 electron removed from the 3s orbital
Na+ 1s2 2s2 2p6
CHLORINE Cl 1s2 2s2 2p6 3s2 3p5 1 electron added to the 3p orbital
Cl¯ 1s2 2s2 2p6 3s2 3p6
ELECTRONIC CONFIGURATION OF IONS
• Positive ions (cations) are formed by removing electrons from atoms• Negative ions (anions) are formed by adding electrons to atoms• Electrons are removed first from the highest occupied orbitals (EXC. transition
metals)
SODIUM Na 1s2 2s2 2p6 3s1 1 electron removed from the 3s orbital
Na+ 1s2 2s2 2p6
CHLORINE Cl 1s2 2s2 2p6 3s2 3p5 1 electron added to the 3p orbital
Cl¯ 1s2 2s2 2p6 3s2 3p6
FIRST ROW TRANSITION METALS
Despite being of lower energy and being filled first, electrons in the 4s orbital are removed before any electrons in the 3d orbitals.
TITANIUM Ti 1s2 2s2 2p6 3s2 3p6 4s2 3d2
Ti+ 1s2 2s2 2p6 3s2 3p6 4s1 3d2
Ti2+ 1s2 2s2 2p6 3s2 3p6 3d2
Ti3+ 1s2 2s2 2p6 3s2 3p6 3d1
Ti4+ 1s2 2s2 2p6 3s2 3p6
ELECTRONICCONFIGURATIONS
THE END
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